Issue 41

V.Shlyannikov et alii, Frattura ed Integrità Strutturale, 41 (2017) 285-292; DOI: 10.3221/IGF-ESIS.41.38 292 C ONCLUSIONS he effects of material damage on the stress field, shape and size of fracture process zone of a mode I creep crack were investigated on the basis of continuum damage mechanics by using multi-axial stress function. Two cases of continuum solids state, i.e. undamaged creeping material and defective material with different degree of creep damage, were examined. A governing parameter of damage field for creeping solids under multi-axial stress state represented by the experimental constant in the form of ratio uniaxial tensile rupture strength to compression at an appropriate test temperature. It has been shown that the creep holding time and multi-axial states of stress may be combined to produce a method on the basis of creep stress intensity factor for quantifying the damage effects on creep crack growth rate. A CKNOWLEDGMENTS he author gratefully acknowledges the financial support of the Russian Science Foundation under the Project 17- 19-01614. R EFERENCES [1] Hayhurst, D.R., Creep rupture under multi-axial states of stress, J. Mech. Phys. Solids, 20 (1972) 381–390. [2] Pisarenko, G. S., Lebedev, A.A., Deformation and Strength of Materials under Complex State of Stress, Naukova Dumka, Kiev, (1976). [3] Hutchinson, J.W., Constitutive behavior and crack tip fields for materials undergoing creep-constrained grain boundary cavitation, Acta Metall., 31 (1983) 1079–1088. [4] He, M.Y., Hutchinson, J.W., in: Elastic-Plastic Fracture, v.1, ASTM STP 803, American Society for Testing and Materials, Philadelphia, (1983) 227–290. [5] Qinghua Meng, Zhenqing Wang, Asymptotic solutions of mode I steady growth crack in materials under creep conditions, Acta Mech. Solida Sinica, 28 (2015) 578–591. [6] Murakami, S., Hirano, T., Liu, Y., Asymptotic fields of stress and damage of a mode I creep crack in steady-state growth, Int. J. Solids Struct., 37 (2000) 6203–6220. [7] Li, F.Z, Needleman, A., Shih, C.F., Characterization of near tip stress and deformation fields in creeping solids, Int. J. Fract., 36 (1988) 163–186. [8] Budden J.P., Ainsworth, R.A., The effect of constraint on creep fracture assessments, Int. J. Fract., 87 (1997) 139–149. [9] Kachanov, L.M., Introduction to Continuum Damage Mechanics, Martinus-Nijhoff, Dordrecht, (1986). [10] Shlyannikov, V.N., Tumanov, A.V., Characterization of crack tip stress fields in test specimens using mode mixity parameters, Int. J. Fract., 185 (2014) 49–76. [11] Shlyannikov, V.N., Tumanov, A.V., Boychenko, N.V., A creep stress intensity factor approach to creep-fatigue crack growth, Engng. Fract. Mech., 142 (2015) 201–219. T T